SIPLens Back to calculatorCalculation methodology
SIPLens uses one deterministic, period-by-period cashflow engine for forward projections and goal calculations. The visualisation is driven by those computed cashflows—not an invented animation.
The entered annual return is treated as an effective annual assumption. For monthly contributions, the engine derives the monthly rate as (1 + annual rate)^(1/12) − 1. Quarterly and weekly modes use 4 and 52 periods respectively. This avoids silently mixing effective and nominal rates.
The default is beginning of period: a contribution is added and then that period’s assumed growth is applied. Advanced assumptions can switch to end of period, where growth is applied before the contribution. This affects the projected value and is therefore never hidden.
Each contribution period has an opening value, any regular contribution and top-up, assumed growth, and a closing value. During a pause, the regular contribution is zero while the existing balance continues along the same smooth mathematical return path.
The contribution amount changes once per completed year by the selected annual percentage. A 10% Step-Up turns ₹10,000 per period into ₹11,000 in year two, then ₹12,100 in year three. The comparison separates extra contributions from estimated growth.
When a target is stated in today’s money, SIPLens first calculates its future nominal equivalent using the entered inflation assumption. A binary-search solver then finds the periodic contribution that reaches that target using the same forward engine, avoiding formula mismatch.
Calculations retain full JavaScript numeric precision and round only for display and exported summaries. Real SIPs buy units at actual NAVs on contribution dates and markets do not deliver smooth periodic returns. SIPLens is an illustration, not a reproduction of real fund behaviour.